He's not an expert doesn't equal he lacks any knowledge whatsoever. He might lack the knowledge to theorise what the bones are used for but has enough knowledge to know that it doesn't work as a muscle attachment point. How is this paradoxical?

That's such a fine point to be that knowledged but just shy of being able to actual speak confidently on the matter. It means they don't have the knowledge to speak confidently on the matter that they just did. Paradoxical.

They don't speak for their own credentials and it's unwise to trust a confident statement made right after saying:
I'm not an expert but...

Its pretty common to be that level of knowledgeable. A lot of people are casually interested enough about animals and biology to have heard discussions about muscular structures that they can determine when something doesn't work. It doesn't mean they can form their own hypothesis on what a spinosaurus skeletal structure is used for, especially if he knows that even experts are still arguing about it until today.

It's wiser to trust the words of someone who knows his own limitations and admits to it than someone who confidently uses a word without knowing the meaning. You can't seem to grasp that people can have a varied level of knowledge about different things within the same subject.

You're basically saying that someone being confident about your car having a puncture is being paradoxical if he also doesn't have the confidence to say what punctured it.

How does paleo art work now? What's done differently?

Headbangosaurus

We know from the bones many things such as the weight the animal could support and how they walked indicating how they balanced. Depending on the age and sediment the animal might have even left a pretty good outline, and in highly alkaline conditions some saponified tissue would remain (completely denatured, but the shape would be there).

The creature in the OP meme for example was a hind-legged walker, so it couldn't be too front heavy and it's front paws weren't heavy weight-bearing. Just like all of it's close relatives who came before and after it.

HOWEVER! This interpretation can change! Originally only two Spinosaurus specimen were collected in very small number of bones with which to make recreations, due to difficulties in and around the region of Egypt. It can be very difficult for archeologists to make digs given their history with the region and the local extremist factions who oppose the concept of things like dinosaurs and ancient cultures. Recently a 2014 study which looked at one particular rock proposed the Spinosaurus tail was webbed, indicating it was semi-aquatic, which would have an impact on weight distribution of the animal and support the idea of a more bouyant build.

Mostly this is just an issue with the nature of science. There's fundamentally just a lot we don't know about what these creatures looked like. Thankfully, in the last 20-30 years, we've learned a lot more. We've become a lot better at finding evidence of feathers and other surface details. We may have gotten better at estimating the musculature? I'm not really sure what the current state of knowledge is here.

But the key thing to consider is that science, as a project, is incredibly conservative. Science is all about precisely defining your claims and clearly justifying them, ideally via quantitative analysis. The reason old renderings of dinosaurs look like this is that these represent the threshold of the known. They are scientific renders, containing only the details that we can be reasonably certain actually existed on these animals. You can of course go further and fill in missing details with imagination and reasonable speculation, but this will always be more an exercise in art than science, a speculative exercise. Yes, dinosaurs likely didn't have this "shrink wrapped" appearance. But what their real appearance was is a guessing game. Yes, it's plausible spinosaurus had big back muscles rather than a fan, but there are likely also other speculative models people could propose. Maybe the spine isn't a fan, but the base of some giant peacock-type tail? Maybe it wasn't a fan, but a series of spikes. Maybe it wasn't one vertical fan, but two horizontal sheets? Who knows?

Science is an inherently conservative exercise. We tend to forget this. Political conservatives hate science because they hate when reality disagrees with their dogma. But while political conservatives call science woke or liberal, the truth is, institutionally, science is conservative. Ideas move slowly. Major paradigm shifts only occur when overwhelming evidence forces them to. Ideas often take decades to slowly percolate through academia, sometimes only changing because the old generation retires or dies of old age.

Scientists as such are, generally, biased against making unfounded claims and speculation. A lot of scientific training focuses on precisely defining your claims, including the precise limits of those claims. And this bleeds over into scientific renderings. From a scientific perspective, it is often better to make a rendering that you know is almost certainly incorrect, rather than make a likely more correct rendering that you cannot support with evidence.

Some recent evidence suggests the Spinosaurus may or may not be semi-aquatic. We've got a super limited fossil record from this region of Egypt.

Party on, Wayne!

Yeah man, but it was a dry heat!

The reason old renderings of dinosaurs look like this is that these represent the threshold of the known. They are scientific renders, containing only the details that we can be reasonably certain actually existed on these animals. You can of course go further and fill in missing details with imagination and reasonable speculation, but this will always be more an exercise in art than science, a speculative exercise.

I feel like a better way to represent "the threshold of the known" would be sort of the pictorial equivalent of "error bars" — instead of doing one image showing an animal that basically looks like it has mange because that's all you can be sure of, do a matrix of images that show various extremes of possibilities.

I'm blanking on the exact phrase, but it's something like "never believe a number with unreported error".

To get further into the weeds there is a significant difference in approach between theoretical and experimental science. In experimental science it's not only enough to communicate what you "know" but to communicate the underlying biased, tolerances and precisions of the thing being measured and modeling approach being used.

these represent the threshold of the known.

I would argue that those representations are inherently bad science because they do not communicate the margin of error. Grue, I believe you are spot on with a concept in how you would make those drawings more scientifically accurate, but ultimately they are artistic renderings of scientific understandings, but not scientific themselves.

While I don't disagree with WoodScientist that modern scientific institutions are inherently conservative, the process of science is not, nor should it be. Apologizing for the inherent conservatism in science is unscientific, harms belief in vetted resulted, conflates institutions for processes and projects a people problem onto the inanimate.

That's just a hairless cat that lost its ears fighting other cats

That's a bison, not a buffalo. Buffalo don't have those humps.

Dude I don’t even know an oboe from an elbow

No. Vastly different levels of complexity and specialization.

You just want to believe Wikipedia deep dives account for actual self knowledge. It just makes them a ke to repeat the arguments of others, not add their own opinion. They didn't say that experts agree it wasn't for muscle attachment they made their own statement regurgitating the words of others.

I'm just not willing to hold undue faith because it makes me feel better.

i'd say these days paleo art is more "okay so we know what related animals look like, and we know what animals in the same general niche look like, so let's use those to fill in the blanks from the skeleton and make something that looks like you could find it in the wild"

honestly i feel like many people are quite a bit too generous towards people of the past, people just really liked to write fanfiction with fossils as the base for a lot of the history of paleontology.. Basically like what jurassic park did but they passed it of as enlightened science, conveniently forgetting to tell people that they just went ahead and moved a bone found near the legs up to the nose..
Certainly there was genuine attempts to recreate dinosaurs, but good lord a lot of it is just obviously biased, lord forbid dinosaurs not be portrayed as sluggish obsolete monsters!

Funny, but afaik/iirc the spine things are more like fins, a bit too thin & they lack big anchoring points for giant muscles (where tendons and ligaments attach to bone). Also they are positioned in the middle of the back, not behind the neck (above the shoulders).

Perhaps they evolved for display, temperature management, or even for swimming maybe. Or a mixture of all.

Or they were just walking ad billboards.